Methods and apparatus for installation and removal of preventer stacks in offshore oil and gas wells



0. BROWN 3,461,958 ION AND' REMOVAL OF WELLS Aug. 19, 1969 c METHODS ANDAPPARATUS FOR INSTALLAT PREVENTER STACKS 1n OFFSHORE OIL Filed Jan. 16,196'? AND GAS s Sheets- -Sheet 1 K o 8 o ATZTORM'] 3,461,958 N ANDREMOVAL OF OFFSHORE OIL AND G Aug. 19,1969

C C. BROWN METHODS AND APPARATUS FOR INSTALLA'I'IO PREVENTER STAGKS INAS WELLS Filed Jan. 16. 196'? s Sheets-Sheet 2 AZTORNE) Aug. 19, 1969 IMETHODS AND APPARATUS mavsmzn s'rAcKs m o C C. BROWN Filed Jan. 16. 1967FOR INSTALLATION AND REMOVAL OF FFSHORE OIL AND GAS WELLS 6 Sheets-Sheet5 ATTORN/fj c c. BROWN 3,461,958

TION AND REMOVAL OF Aug. 19, 1969 METHODS AND APPARATUS FOR INSTALLAPREVENTER STACKS IN OFFSHORE OIL AND GAS WELLS Filed Jan. 1 s. 1967- sSheets-Sheet 4 Z 2 i VA 7 f L M HU ML a E. \t w z W a. 5 z 2 in; m w m aM w w w m, w ll! a a M a fv ll'l V.

'6 Sheets-Sheet 5 C C. BROWN -PREVEN'IER STACKS IN OFFSHORE OIL AND GASWELLS METHODS AND APPARATUS FOR INSTALLATION AND REMOVAL OF Filed Jan.16. 196'! Aug. 19, 1969 c Q 3,461,958

METHODS AND APPARATUS FOR INSTALLATION AND REMOVAL OF PREVENTER STACKSIN OFF WELLS Filed Jan. 16. 1967 6 Sheets-Sheet 6 SHORE 011, ND GASATTORNEY United States Patent METHODS AND APPARATUS FOR INSTALLATION ANDREMOVAL OF PREVENTER STACKS DI OFFSHORE OIL AND GAS WELLS Cicero C.Brown, Brown Oil Tools, Inc., P.0. Box 19236, Houston, Tex. 77024 FiledJan. 16, 1967, Ser. No. 609,572 Int. Cl. E21b 33/035, 33/06 US. Cl.166.5 Claims ABSTRACT OF THE DISCLOSURE Summary of problem and inventionThis invention relates to a method and means for installing preventerstacks in underwater wells for ease of removal, and further relates to amethod and means providing recovery of preventer stacks and associatedapparatus.

It is readily apparent that drilling oil and gas wells is an' expensiveproposition, and this is especially true in offshore operations. One wayof holding the cost of drilling operations to a minimum is the recoveryof as much equipment installed in or at the drilling site as possible,and especially so in recovering the more expensive apparatus used inoffshore operations. One of the more expensive items required indrilling oil and gas wells is the stack of blowout preventers. Blowoutpreventers are installed at the well head to limit upward flow throughthe well bore and also to prevent upward movement of the drill stringshould the drill bit enter a formation having exceedingly high internalpressures. High pressure formations suddenly penetrated by the well borehave ejected the drill string upwardly through the well head to causesubstantial damage to the drilling equipment and serious injuries to thepersonnel. The problem is also present in drilling operations inoffshore locations where the preventer stack is installed beneath thebody of water at the well head.

In all drilling operations, the drilling operation is eventuallyterminated and the blowout preventers are removed from the well. This istrue whether the well is a dry hoe or provides oil in substantialquantities. The method of removing blowout preventers from the offshorewells has been less than successful. The preventer stack is customarilyjoined to the casing and a protector casing placed about the casingstring. In view of the substantial length of protecter casings, and infurther view of the fact that the well casing extends several thousandfeet in the well, the preventer stack is usually firmly cemented inplace and difiicult to recover.

One method found in the prior art requires upward lifting forces on thepreventer stack to free the preventer stack from the casing and thepreventer casing which are 3,461,958 Patented Aug. 19., 1969 "icecemented in place. In view of the limitations of the prior art, thepresent invention may be summarized as providing a pressure fluidexpansion chamber below the preventer stack for lifting the stack fromthe well on admission of pressure fluid through the well casing. Thechamber is not used until the preventer stack is no longer needed atwhich time fluid communication between the well head and chamber isestablished. Pressure fluid in the chamber acts against a surface tolift the preventer stack. The chamber expands by use of a sliding sealpermitting continued admission of pressure fluid to substantially liftthe appendages to the preventer stack free of the well. With the presentsummary in view, it is, therefore, an object of the present invention toprovide a method of installing and removing preventer stacks inunderwater wells in which the separation of the preventer stack from thecasing is achieved by pressure fluid lifting the preventer stack.

A related object of the present invention is to provide a new andimproved apparatus for recovery of preventer stacks from underwaterwells wherein the drilling vessel lifts only the preventer stack and isnot used to free the frictional engagement of the cement jacket with thewell bore.

One object of the present invention is to provide a new and improvedmethod for installing and removing preventer stacks in underwater wellswherein separation between the preventer stack and well casing isachieved by disconnection as opposed to rupture of the well casing andcement jacket.

Yet another object of the present invention is to provide a new andimproved method for recovering preventer stacks from underwater wellswherein movements against substantial friction between the cement jacketand the well bore is achieved by hydraulic pressure supplied to the wellto lift the preventer stack.

One object of the present invention is to provide a new and improvedmethod of retrieving preventer stacks in which the annulus between theprotector casing and well casing is used as an expansion chamber forlifting the preventer stack from below to avoid damage to the expensiveapparatus.

Yet another object of the present invention is to provide a new andimproved method of removing preventer stacks from underwater wells inwhich the installation is effected with a view of easy removal withoutinterfering with the function of the blowout preventers or drilling ofthe well.

One object of the present invention is to provide a new and improvedapparatus for removing installed blowout preventers from underwaterwells which incorporates means for freeing the well casing from thepreventer stack and thereafter uses a chamber for receiving pressurefluid to lift the preventer stack from the well.

Other objects and advantages of the present invention will become morereadily apparent from a consideration of the specification and drawingswherein:

FIG. 1 is a longitudinal sectional view of the apparatus of the presentinvention during assembly on a drilling vessel before placement in thewell bore;

FIG. 2 is a longitudinal sectional view similar to FIG. 1 after assemblyand prior to placement in a well bore;

FIG. 3 is a longitudinal sectional view of the apparatus shown in FIGS.1 and 2 after cementing in the well bore which further illustratesoperation of a tool to separate the casing from the preventer stack;

FIG. 4 is a view similar to FIG. 3 showing the step of separating thecasing from the preventer stack and further illustrating pressure fluidflow for lifting the preventer stack;

FIG. 5 is a view similar to FIG. 4 illustrating completion of the stepof lifting the preventer stack;

FIG. 6 is similar to the step shown in FIG. 3 and also illustrates analternative embodiment of the present invention;

FIG. 7 illustrates an additional step in the method using the embodimentshown in FIG. 6;

FIG. 8 is a sectional view of an additional embodiment of the presentinvention showing use of an inside cutter for separating the preventerstack from the well casing;

FIG. 9 is similar to FIG. 8 and illustrates separation of the preventerstack from the well casing;

FIG. 10 illustrates an additional embodiment of the present invention;and

FIG. 11 is a view similar to FIG. 10 illustrating the preventer stackduring the step of lifting the preventer stack while the protectorcasing remains in the cemented Well bore.

Attention is first directed to FIGS. 1-5, inclusive, which illustratethe method and apparatus of the present invention in detail. Theapparatus associated with FIGS. 1-5 will be first described, andthereafter, the steps of the method of the present invention will bealso related, particularly with reference to the drawings whichillustrate various steps in the method. Therefore, attention is firstdirected to FIG. 1 of the drawings which illustrates the apparatus in astate of assembly prior to installation in a well bore.

In FIG. 1, a joint of casing 12 is preferably integrally joined to atubular connector 11 for use in making up the casing string to be placedin the well bore (not shown). The connector 11 is held in apredetermined position by resting a flange 13 on a removable support 10,the support 10 customarily located on the drilling barge or vessel inthe water near the drilling site of the well.

Aboard the drilling vessel, the upper portions of the well casing stringare assembled relative to the protector casing as will be described. Infurther particular, a base member 16 serves as mounting means for theblow-out preventers 20 which are located thereabove and as a support fora casing member 12a suspended therebelow. Positioned concentricallyabout the casing member 12a is a protector casing which is somewhatgreater in length than the casing 12a.

In drilling oil and gas wells located beneath bodies of water, theprotector casing 15 length is varied over a wide range depending on theconditions encountered. Thus, for instance, the preventer casing may berelatively short should solid, non-porous geological strata beencountered. The members 12a and 15 are arranged concentrically of oneanother and have a length best determined by conditions at the drillingsite.

Considering the blow-out preventers further, attention is directed toFIGS. 1 and 2 which illustrate the preventers secured to the upper sideof the base plate 16. In the drawings, the preventer stack is secured tothe base plate by conventional bolts 20a and a seal member is placedinteriorly of the bolts 20a for maintaining a pressure tight seal. Therams of the preventer stack are represented generically in the drawingsas will be understood by those skilled in the art.

Attention is next directed to the means indicated generally at 18 at thelower end of the casing member 12a which comprises a male connectormeans for releasable connection with the tubular member 11. A settingsleeve 22 is threaded into the lower end of the casing member 12a, itbeing noted that the casing member is somewhat enlarged at the threadedconnection whereby the setting sleeve is equal in inside diameter to thecasing member 12a and the connector member 11 therebelow. The settingsleeve 22 incorporates conventional seal means at both 4 ends thereof toprovide integrity of fluid communication through the well casing string.Of particular interest is the expander ring 23 adjacent the settingsleeve which is in a relaxed condition in FIG 1. Use of the expanderring 23 will be noted in greater detail hereinafter.

Attention is next directed to the tubular connector means 11 engagedwith the male connector means 18. The means 11 incorporates theoutwardly extending shoulder means 11a for engaging additional meansplaced within the protector casing 15 as will be described. An internalrecess 11b is provided within the connector means 11 for receiving theexpander ring 23. A sealing surface 11c within the connector is providedfor engaging the seal member on the setting sleeve 22 to maintain fluidcommunications through the well casing string. Additional detailsconcerning the female connector member 11 will be noted hereinafter.

Attention is next directed to the apparatus carried within the protectorcasing 15 and engaging the shoulder 11a on the connector member 11.Attention is first directed to the encircling resilient cup 28 which isheld in position by a support ring 29. The support ring 29 is carried bythe shoulder 11a on upward movement of the shoulder relative to theprotector casing 15 whereby the rubber ring 28 is sealed against theinterior wall of the member 15. A retainer ring 15a is engaged at theloWer end of the protector casing 15 for initially inserting the sealcup 28 within the casing member 15. The ring 15a is threaded to theinterior of the casing member 15.

It should be noted that the foregoing description is directed to thedetails of construction of the apparatus shown arranged in FIG. 1.However, the apparatus of FIG. 1 is also illustrated in FIGS. 2-5,inclusive, during various stages in the practice of the method of thepresent invention. Relying on the foregoing description of theapparatus, attention is next directed to FIGS. 1-5 for an understandingof the method of the present invention. FIG. 1 illustrates the assemblystage of the present method. The setting sleeve 22 is threaded to thelower end of the casing member 12a and thereafter the protector casing15 is positioned in the concentric relationship illustrated in thedrawings relative to the casing 12. The cup 28 is placed within theprotector casing 15 and the retainer member 29 is inserted thereafterand the two members are locked within the protector casing by theretainer ring 15a. The female connector means 11 is placed in protectorcasing 15 about the setting sleeve 22 as shown in FIG. 1. Upwardmovement of the shoulder 11a urges the support ring 29 and the rubbercup 28 to the illustrated position of FIG. 1 wherein the femaleconnector is positioned for later engagement with the male connector.

Attention is next directed to FIG. 2 of the drawings which illustratesthe step of the present method wherein the tubular connector 12a whichcarries the preventer stack 20 is joined to the casing string 12. Atorque-wrench 34 is inserted through the preventer stack 20 andpositioned adjacent the setting sleeve and engaged therewith. Thesetting sleeve is preferably provided with left-hand threads engaginginterior threads of the connector means 18. The setting sleeve fullythreads against an abutting shoulder 18a illustrated in FIG. 2.

Attention is next directed to the expander ring 23 which is in theexpanded position in FIG. 2. The expander ring 23 is forced into theinternal recess 11b of the female connector means 11 which is positionedadjacent the expander ring, the extreme end 18b of the tubular member 18moving beneath the ring to expand it into the recess 11b. It will benoted that the two portions of the casing string, the members 11 and 18in particular, have been joined to one another by the expander ring 23.Reference is made to the fact that the recess 11b is defined by a pairof facing shoulders which lock the expander ring 23 in place.

In the assembly step shown in FIG. 2, it should be noted that theconnccter members 11 and 18 are moved axially toward one another bythreaded engagement with the setting sleeve 22. The movement contactsthe flanges 13 carried on the connecter 11 against the open lower end ofthe casing 15 and provides an adequate seal to prevent intrusion ofmaterials under pressure into the annulus between the two casingmembers.

At this juncture, the support member is removed and the preventer stack,including the casing 12, is inserted into the hole drilled beneath thedrilling platform or vessel. Attention is next directed to FIG. 3 whichillustrates the preventer stack and casing string in the well bore. Theprotecter casing is cemented within the well bore 36 which has anenlarged diameter sufliciently deep to accommodate the enlargedprotector casing 15. The casing string 12 is also cemented in place at37 to an adequate depth. The base plate 16 is rested on the floor of thebody of water.

At some point in time in the drilling operations conducted through thewell casing 12, it becomes necessary to either plug the well prior toabandonment or to remove the preventer stack because production has beenobtained. Using the well plug as an example of terminated drilling,known techniques are used to insert a cement plug 38 in the well casing12. A reversing tool 46 is run into the casing string and positionedadjacent the setting sleeve 22 preliminary to disengaging the preventerstack from the well casing string. The reversing tool 46 is used todisengage the setting sleeve for release of the connectors 11 and 18.

Attention is redirected to FIG. 1 which illustrates the male connectermeans 18 as including a plurality of ports 182. The ports 18e areadjacent the shoulder 18a whereby communication from the interior of thecasing string 12 is obtained to the annulus thereabout when the settingsleeve 22 is in the partially threaded position of FIG. 1. Conversely,FIG. 2 illustrates complete engagement of the setting sleeve 22 wherebythe ports 18e are sealed against communication from the casing string12. The ports 18e are sealed during the drilling operations until thetermination of drilling.

Attention is next directed to FIG. 4 which illustrates the use of theports 18e after the reversing tool 46 has returned the setting sleeve tothe position illustrated in FIG. 1. The downward movement of the settingsleeve relative the connecter means 18 exposes the ports 18e forcommunication from the casing string into the annulus defined by theprotector casing 15. The annulus or chamber, indicated by the numeral50, is defined by the protector casing 15, the casing member 12a, andthe base plate means 16. The base plate means 16 provides a surfacewhich communicates upward force to the preventer stack 20 onaccumulation of fluid in the chamber 50 under pressure. The chambermeans 50 is particularly defined by the facing walls of the casingmembers 12a and 15 which extend downwardly to the rubber cup 28 carriedon the support ring 29. The rubber cup 28 is constructed and arranged torespond to pressure fluid in the chamber means 50 to slidingly sealagainst the wall of the preventer casing 15.

A closed fluid system is defined within the casing string for receivingpressure fluid from the drilling platform or vessel. In this regard,attention is directed to the reversing tool 46 which is retained in thewell bore after disconnection of the setting sleeve 22 between the maleand female connectors 18 and 11, respectively (see FIG. 4). Thereversing tool 46 includes a plurality of ports 46a communicating with atubing string 48 for directing pressure fluid to the well annulus 50. Apair of rams 20b are positioned against the exterior of the tubingstring 48 to seal the casing string 12 against flow upwardly in thestring. Pressure fluid is delivered through the tubing string 48 asindicated by the arrows 52. The pressure fluid passes through the ports46a and the reversing tool 46 and is limited in upward or downwardescape in the well casing by the 'cement plug 38 and the rams 20 of thepreventer stack means. The constraints on flow limit the fluid topassage through the ports 18:: into the annulus means 50.

On delivering an adequate quantity of pressure fluid to the chamber 50,the pressure fluid acts upwardly against the base plate 16 to provide anaxial strain upwardly on the casing members 12a and 15. Since the casingmember 12a was disengaged from the casing string 12 by setting sleeves22, the member 12a is free to move upwardly with the base plate 16.Likewise, the protector casing 15 is not joined to the casing string 12at the flange 13, but merely rests thereon for relatively easydisengagement as shown in FIG. 4. The casing member 15, joined to thebase plate 16, imparts a failure circumferentially of the cement at theflange plate 13. A substantial force is required for this failure,although it will also be appreciated that cement is inherently weak intension and therefore fails without requiring excessive axial strain onthe casing 15.

The step of pumping pressure fluid into the tubing string 48 iscontinued indefinitely until the tubular portion con nected to thepreventer stack breaks free of the cement bond with the open hole 36.

As noted above, the step of pumping pressure fluid into the chamber 50is continued whereby the seal cup 28 slides axially toward the lower endof the protecter casing 15 as the tubular members attached to thepreventer stack 20 are expelled from the well bore under pressure. Thisstep is represented in FIG. 4 and FIG. 5 wherein the upward movementfrees the seal cup member 28 and the support ring 29 from the lowerconnecter 11. At this point, with the protector casing 15 substantiallyexpelled from the well bore, and with reduced frictional engagement withthe well bore, the preventer stack is easily retrieved by the drillingplatform or vessel.

Attention is next directed to FIGS. 6 and 7 which illustrate analternative method of the present invention. The steps of installing thepreventer stack in the well (as illustrated in FIGS. 1 and 2) areomitted, but reference is made to the foregoing description forunderstanding of the method presently omitted. FIG. 6 is generallysimilar to FIG. 3 in illustrating a plug in the casing after the wellhas been abandoned.

The apparatus illustrated in FIG. 6 which bears a similarity to theapparatus shown in FIGS. 1-5, inclusive, bears the identical referencenumerals increased by one hundred, and the foregoing description isadequate for FIGS. 6 and 7. In FIG. 6, an inside cutter tool means 146is run in the casing string 112, and positioned adjacent the settingsleeve 122. Those skilled in the art will appreciate the somewhatschematic representation of the cutter tool 146 which carries thecutting elements 146a against the setting sleeve 122. The setting sleeve122 is shown in FIG. 6 in the locking position whereby the tubularmembers 112a and 111 are joined to one another by expansion of theexpander ring 123 into the locking position previously illustrated inFIG. 3. The tool means 146 is positioned with the cutting elementsimmediately adjacent the setting sleeve 122 whereby the cutters 146a aregradually extended as the tool is rotated to form an ever. deepening cutcircumferentially interiorally of the setting sleeve 122. When thecutters extend fully through the setting sleeve, the cutting blades areretracted, permitting separation of the male and female connectors 118and 111, respectively. It should be noted that the cut the settingsleeve not only destroys the structural integrity of the joint andeffects a disconnection in the well'j casing string, but the cut alsoprovides access from the interior of the casing string to the annulusfor admission of pressure fluid. The chamber means 150 operates in thesame manner as the chamber means 50 above noted. At this juncture,reference is made to FIG. 7 which illustrates the next step of thepresent method.

The cutter tool 146 communicates pressure fluid through the tubingstring 148 axially of the well string. Again, sealed means are effectednear the well head, and for purposes of illustration, the rams of thepreventer stack 120 are extended to seal off the well casing stringagainst upward flow of fluid. The fluid passes through the tubing string148 and the cutter head 146 into the cut about the circumference of thesetting sleeve 122. Reference is made to the separated portions of thesetting sleeve attached to the connectors 111 and 118. When the pressurefluid admitted through the tubing string 148 fills the chamber 150 andacts against the base plate means 116, the lifting force on thepreventer stack 120 moves it upwardly. Also, the protector casing 115 islifted upwardly and expelled from the well bore 136. Upward movement ofthe protector casing imparts circumferential break to the cement aboutthe protector casing 115.

The upwardly movement of the base plate 116 and associated tubularmembers expands the chamber means 150 by moving the seal cup 128 alongthe wall of the protector casing 115 to maintain fluid integrity withinthe chamber means 150. Upward movement of the protector casing 115 isaccompanied by upward movement of the casing segment 112a as thepreventer stack 120 is retrieved. Hydraulic retrieval of the preventerstack is continued until the preventer stack and tubular segmentsassociated therewith are substantially expelled from the well bore 136whereupon the friction of the cement jacket against the well bore 136 issubstantially reduced. The preventer stack is lifted by conventionalapparatus aboard the drilling barge or vessel. Reference is made toFIGS. 4 and 5 associated with the previously described method forillustration of the last steps of the method of the present invention.

Attention is next directed to FIGS. 8 and 9 of the drawings whichillustrates an additional alternative in the method of the presentinvention. Apparatus similar to the apparatus previously noted in FIGS.1-7, inclusive, bears numerals increased by one hundred. In FIG. 8, thepreventor stack means 220 is mounted on the base plate 216, and thecasing member 212a is connected to the casing string 212. In addition,the protector casing 215 is placed thereabout and joined to the baseplate 216. The casing 215 extends longitudinally of the casing string212 and rests on a flange plate 213 integrally formed with the casingmember 212a.

Of particular interest and contrast in the apparatus shown in FIGS. 8and 9 is the fact that connecters (see connecters 18 and 11 in FIG. 1)are absent from the embodiment. While no connector means are specified,connection of the casing string to the base plate 216 has the form ofintegral construction for purposes of the claims. The chamber means 250is defined by the lower face of the plate 216 and the annulus betweenconcentric tubular members 212a and 215. The lower end of the chambermeans 250 is defined by the seal cup 228 which is a circumferential sealcarried on the support ring 229. Of particular interest is the variationshown in FIG. 8 wherein the seal support ring 229 is integrally formedwith the tubular member 212a comprising a portion of the casing string.While the support ring 229 is illustrated as an integral portion of thetubing string, it will be appreciated that the support ring may bewelded or otherwise joined to the casing string. At any event, thesupport ring 229 carries the seal cup 228 against the interior of theprotector casing 215 whereby the chamber means 250 is delimited forreceiving pressure fluid therein.

The method of installation in the well bore of the completed assemblyshown in FIG. 8 is preferably the same as the foregoing describedmethods. An inside cutter tool 246 is run on the tubing string 248 forcutting the casing portions 212:: into two segments, an upper segmentabove the cut at 218 and a lower segment below the cut which is leftwith the remainder of the casing string. The inside cutter tool 246 is aconventional device known to those skilled in the art. After cutting,the cutter blades 246a are retracted and the casing string is sealedthereabove, perhaps near the well head, preferably by use of the blowout preventer means 220 as illustrated in FIG. 9. At this juncture, thedevice is ready for admission of pressure fluid through the tubingstring 248 and the cutting tool 246.

The pressure fluid fills the casing above the plug 238 and also fillsthe chamber means 250 previously described. The chamber means is filledto the base plate 216 and an increase in pressure in the chamber means250 lifts the base plate 216 and the preventor stack 220. The cementjacket joined to the protector casing 215 is fractured near the flangeplate 213. As in the previous embodiments noted hereinabove, the sealcup 228 permits expansion of the chamber means 250 but maintainspressure within the chamber means 250 for further expansion. Afterelongation of the chamber means 250, the seal means 228 is disengagedfrom the protector casing 215 when the preventor stack 220 has beensubstantially lifted free of the well bore 236. Then, conventionallifting apparatus on the drilling barge or vessel is used to recover thepreventor stack 220.

Attention is next directed to FIGS. 10* and 11 which illustrate furthermodifications of the method and apparatus of the present invention. InFIG. 10, the apparatus is again shown in the assembled condition in thewell bore and reference is made to the foregoing descriptions for anunderstanding of the method of assembly and placement in the well bore.At the illustrated step of the present method, FIG. 10 shows anabandoned well with a plug 338 in the casing 312. As in the previousdescriptions, similar parts have reference numerals similar topreviously used reference numerals, increased by one hundred. The casingstring is joined or connected to the preventer stack means 320 by thecasing member 31211 which eX- tends from the base plate 316 to thecasing string 312. The member 312a is welded or otherwise joined to thebase plate 316 as will be noted in the drawing. The flange 313 on thecasing string 312 supports the protector casing 315 which is Weldedthereto in the preferred embodiment. Of particular interest is the factthat the casing 315 is not joined to the base plate 316 as described inpreviously noted embodiments.

The apparatus shown in FIGS. 10 and 11 also incorporates a seal cup 328which is carried on a laterally extending support member 329. Ofparticular interest in this embodiment is the fact that the sealed means328 is located relatively high adjacent the protector casing string. Theseal support 329 is preferably welded or integrally formed with casingmember 312a. The high location of the seal means 328 defines a chambermeans 350 therebelow extending to the flange plate 313. Again, thechamber means 350 is located in the annulus between the concentrictubular members 312a and 315. The nether side of the support member 329provides a surface communicating upward lifting force from pressurefluid in the chamber 350 to the preventer stack 320. While thepreviously described embodiments utilize the base plate to communicateupward lifting to the preventer stack, the present invention utilizesthe lower side of the support 329 which communicates the upward force tothe tubular member 312a for lifting the preventer stack upwardly.

An inside cutter tool 346 carried on a tubing string 348 is run in thecasing string after the cement plug 348 has been placed therein forcutting the well casing as illustrated.

The cutting tool 346 carries conventional cutters 346a extended to formupper and lower portions, it being noted that the upper portion isjoined to the preventer stack 320 and the lower portion remains with thecasing string 312. Reference is made to FIG. 11 of the drawings whichillustrates the use of the tubing string 348 as a conduit for pressurefluid supplied from the drilling barge or vessel. Again, provision ismade for some sort of seal means near the well head for maintaining thepressure fluid in the well casing string for admission to the chambermeans 350. In any case, the pressure fluid is admitted through thetubing string 348 and is exhausted through the inside cutter tool 346 atthe cut 318 which forms a passage means communicating through the wallof the casing string into the chamber means 350. The pressure fluid isadmitted thereto and on increase of pressure, acts upwardly against thesupport member 329 and communicates an upward lifting force to thetubular member 312a which is imparted to the preventer stack carried onthe base plate 316. The base plate 316 is lifted free of the protectorcasing 315 since the protector casing is not joined structurally to thebase plate 316 as in the previous embodiments.

FIG. 11 illustrates substantial upward expulsion of the casing portion312a and the preventer stack 320 as a' means of recovery of thepreventer stack. Again, continued addition of pressure fluid to thechamber means 350 is dependent on the seal means 328 engaging the casing315. The preventer stack means 320 is freed of the well and retrieved tothe drilling barge or vessel by conventional lifting apparatus. Incontrast to the foregoing methods, it will be noted that the protectorcasing is left essentially intact and in the well bore joined to thecement jacket. By way of further contrast, it will be noted that theseal cup is recovered by the method presently described whereas thepreviously described methods left the seal cup and support member in thewell bore.

While the foregoing describes the various methods utilizing theapparatus of the present invention, it will be appreciated that thescope of the present invention is defined by the claims appended hereto.

What is claimed is:

1. A method of installing and removing preventer stacks in underwaterWells in which a protector casing is cemented in an open hole and a wellcasing is placed therein which comprises the steps of:

(a) Threadedly connecting the preventer stack to the well casing bymeans of a tubular connector;

(b) Forming a pressure fluid tight chamber below the preventer stack;

(c) Said chamber being defined by a surface communicating upward forceto the preventer stack on admission of pressure fluid to the chamber;

(d) Disconnecting the well casing from the preventer stack at a pointbelow the preventer stack by unscrewing said tubular connector;

(e) Pumping pressure fluid into the chamber for lifting the preventerstack upwardly on expansion of the chamber; and

(f) Extending the step of pumping pressure fluid into the chamber untilthe preventer stack and the tubular portion remaining connected theretobreak free of the bond with the open hole.

2. The method of claim 1 wherein the step of forming the pressure tightchamber below the preventer stack includes the step of sealing theprotector casing to the preventer stack.

3. The method of claim 1 wherein the step of forming the pressure tightchamber below the preventer stack includes the step of forming a seal inthe annulus between the well casing and the protector casing.

4. The method of claim 1 wherein the step of pumping pressure fluidincludes the steps of providing a path for fluid flow through the wellcasing into the pressure fluid tight chamber, pumping fluid down thewell casing, directing the fluid along the path provided therefor.

5. The invention of claim 1 including the step of using an inside wrenchto place a setting sleeve in the well casing to connect the preventerstack to the well casing, and simultaneously closing openings in thewell casing communicating with the annulus.

6. The method of claim 1 wherein the step of joining the preventer stackto the well casing is followed by cementing the protector casing in thewell bore.

7. An apparatus for installing preventer stacks on under-water wells,comprising:

(a) A tubular connector extending downwardly from the preventer stack,said connector being adapted to be connected to a well casing for use ina casing string;

(b) Chamber means defined by the well casing and exteriorly thereof;

(c) Said chamber means being at least partially defined by a cylindricalsurface of predetermined longitudinal extent;

(c Seal means slidably and sealingly engaging said cylindrical surfacefor confining fluid pressure admitted to said chamber, said surfacecommunicating upward force on the preventer stack moving in response toincreased pressure in said chamber means, and said surface movement alsoexpanding said chamber by slidably moving said cylindrical surfacerelative to said seal means;

(d) Closable passage means for communicating pressure fluid to saidchamber means to increase the pressure therein; and

(e) Means for disconnecting the preventer stack from the well casing tofree same for movement in response to admission of pressure fluid tosaid chamber means acting against said surface.

8. An apparatus for installing preventer stacks on underwater wells,comprising:

(a) A tubular connector extending downwardly from the preventer stack,said connector being adapted to be connected to a well casing for use inthe casing string;

(b) Chamber means defined by the well casing and exteriorly thereof;

(c) Said chamber means being at least partially defined by a surfacecommunicating an upward force on the preventer stack on increase ofpressure in said chamber means;

(d) Closable passage means for communicating pressure fluid to saidchamber means to increase the pressure therein;

(e) Means for disconnecting the preventer stack from the well casing tofree same for movement in response to admission of pressure fluid tosaid chamber means acting against said surface;

(f) The nether side of the preventer stack being sealingly joined to aprotector casing to at least partially define said chamber means;

(g) A plurality of openings in the well casing; and

(h) Setting sleeve means in the Well casing adapted to be positionedopposite said openings for closing said openings.

9. An apparatus for installing preventer stacks on underwater wells,comprising:

(a) A tubular connector extending downwardly from the preventer stack,said connector being adapted to be connected to a well casing for use inthe casing string;

(b) Chamber means defined by the Well casing and exteriorly thereof;

(0) Said chamber means being at least partially defined by a surfacecommunicating an upward force on the preventer stack on increase ofpressure in said chamber means;

(d) Closable passage means for communicating pressure fluid to saidchamber means to increase the pressure therein;

(e) Means for disconnecting the preventer stack from the well casing tofree the same for movement in response to admission of pressure fluid tosaid chamber acting against said surface;

(f) Said tubular connector being releasably connected to well casing byan axially movable setting sleeve, and the connecting position of saidsetting sleeve closing said passage means.

10. In underwater wells, the method of removing a preventer stack from awell casing which is cemented in place in a well bore, comprising,

(a) Forming a closed chamber about a portion of the well casing belowthe preventer stack by means providing a side wall concentric with saidcasing portion and longitudinally spaced end walls one of which fixedlyconnects said side wall to said casing portion and the other of whichdefines a slidable seal between said side wall and said casing portion,

(b) Severing said casing portion at a point between said end walls, and

(0) Introducing pressurized fluid into said chamber to elevate thesevered upper section of said casing portion carrying the preventerstack relative to the casing section remaining in the well bore.

References Cited UNITED STATES PATENTS Le Rouax 166--.5 Newsome l66-.5Smith 166.5 Johnson 166.6 Pittman et al 166.5 X

Marion 166.6

U.S. Cl. X.R.

